gmaw principles
Post on 17-Jan-2016
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GMAW PrinciplesGMAW Principles
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GMAW Definition GMAW Definition
• GMAW stands for Gas Metal Arc Welding
• A solid metal wire is fed through a welding gun and becomes the filler material
• Shielding gas is used to protect the molten puddle from the atmosphere which results in a weld without slag
GMAW is the most widely used arc welding process in the United States
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GMAW CircuitGMAW Circuit
• Three things happen when the GMAW gun trigger is pulled:– The wire electrode
begins to feed– The circuit becomes
electrically ‘hot’– Completes the circuit
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GMAW Components GMAW Components
• Let’s look a little closer at the GMAW process
Travel direction
Electrode
1Arc2
Weld Puddle
3
Shielding Gas4
5Solidified Weld Metal
Generally, drag on thin sheet metal and push on thicker materials
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1 - Electrode1 - Electrode
• A GMAW electrode is:– A metal wire – Measured by its
diameter
GMAW electrodes are commonly packaged on spools, reels and coils ranging from 1lb to 1000lbs
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2 - Arc2 - Arc
• An electric arc occurs in the gas filled space between the electrode wire and the work piece
Electric arcs can generate temperatures up to 10,000°F
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3 - Weld Puddle3 - Weld Puddle
• As the wire electrode and work piece heat up and melt, they form a pool of molten material called a weld puddle
• This is what the welder watches and manipulates while welding .045” ER70S-6 at 400 ipm wire feed
speed and 28.5 Volts with a 90% Argon/ 10% CO2 shielding gas
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4 - Shielding Gas4 - Shielding Gas
• GMAW welding requires a shielding gas to protect the weld puddle
• Shielding gas is usually CO2, argon, or a mixture of both
The gauges on the regulator show gas flow rate and bottle pressure
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5 - Solidified Weld Metal5 - Solidified Weld Metal
• The welder “lays a bead” of molten metal that quickly solidifies into a weld
• The resulting weld is slag free
An aluminum weld done with the GMAW process
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Application ActivityApplication Activity
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GMAW Components Application Activity
GMAW Components Application Activity
• 1 __________
• 2 __________
• 3 __________
• 4 __________
• 5 __________
• Let’s review the GMAW process
Travel direction
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3
4
5
Generally, drag on thin sheet metal and push on thicker materials
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Striking an Arc and Making a Weld
Striking an Arc and Making a Weld
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Laying a BeadLaying a Bead
The appearance of the puddle and ridge where molten metal solidifies indicates correct travel speed. The ridge should be approximately 3/8” (10 mm) behind the wire electrode.Most beginners tend to weld too fast resulting in a ropey bead which means SLOW down!
The appearance of the puddle and ridge where molten metal solidifies indicates correct travel speed. The ridge should be approximately 3/8” (10 mm) behind the wire electrode.Most beginners tend to weld too fast resulting in a ropey bead which means SLOW down!
• Maintain a Contact Tip to Work Distance (CTWD) of 3/8” to 1/2”
• Use a uniform travel speed• Most Importantly – Watch the Puddle!
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Fill the CraterFill the Crater
• Fill the crater by pausing or using a slight back step
• Release gun trigger and pull gun away from the work after the arc goes out
• Large craters can cause weld cracking
Crater cracks cannot be tolerated on NASCAR radiators.
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